Alternating-current electromagnet



Patented May 4, 1926 PERCIVAL FRANK HARRIS, OF SOUTH SHIELDS, ENGLAND,ASSIGN OR TO A. REYROLLE PATENT OFFICE.

86 COMPANY LIMITED, OF HEBBURN-ON-TYNE, DURHAM, ENGLAND, A BRITISHCOMPANY.

ALTERNATING-GURRENT ELECTROMAGNET.

Application filed April 9, 1924. Serial No. 705,311.

To all whom it may concern:

ms, a subject of the King of England, and

residing at South Shields, in the county of Durham, England, haveinvented certain new and useful Improvements in Alternating-CurrentElectromagnets, of which the following is a specification.

This invention relates to alternating current electromagnets and hasparticular reference to the iron cores and armatures or like cooperatingparts of electromagnets used in alternating current relays orcontact-ors.

The object of the invention is to avoid what are often called chatteringand sticking between the two members between which mutual attractionexists when the electromagnet is energized. The chattering whilstobjectionable on account of the noise produced is also disadvantageousas it may involve bad electrical contacts when, as in a relay, a circuitis controlled. Unnecessary wear of the moving parts is also liable tooccur. The sticking introduces inaccurate operation of the device.

The use of a small pin or point of nonmagnetic material as a separatorbetween the armature and the pole of an electromagnet is a well knowndevice for preventing sticking but it does so by preventing the twomagnetic members from coming into actual magnetic contact and thusincreases the power necessary to produce the requisite operatingmagnetic flux.

According to the present invention one or both of the surfaces of thecooperating mag netic members is formed with one or more points, ridgesor small area surfaces which whilst making magnetic contact with thecooperating surface, prevent the two main surfaces from touching overtheir main areas.

The points, ridges or small area surfaces may be formed in anyconvenient way. For instance if a core is laminated, some of thelaminations may be made to project slightly beyond the main face of thepole or poles, the ridges thus produced being divided in their length ornot.

Again the points, ridges or the like may be tapered in vertical sectionso that the length of the air gap around the points of contact is notuniformover the whole face Be it known that I, PEROIVAL FRANK HAR- aarea.

The accompanying drawings show by way of example various ways in whichthe invention is applied to alternating current electromagnets.

Figure 1 is a side elevation of one con struction, and I Figures 2, 3,4, 5 and 6 are perspectlve views of portions of other constructions.

In all the figures only the magnetic members, 1. e. the cores andarmatures or portions thereof, are shown, the windings of the magnetsbeing omitted as the invention is not concerned with them.

With reference first to Figure 1, A is the pole of an electromagnet andB its armature. The surface of the armature adjacent to the pole is soformed that there is only contact between them at the point B.

In Figure 2 two poles A are indicated and the armature is formed withridges B so that there is only line contact between the cooperatingsurfaces of the poles and the armature.

The portion of the armature shown in Figure 3 has intersecting V-shapedgrooves 13 which have the effect of forming a series of pyramidalprojections B on the surface of the armature. Thus the armature willtouch the pole face at a number of points over its surface.

In Figure 4 the armature has certain of the strips or laminations B ofwhich it is formed of greater depth than the rest so that they projectfrom the surface adjacent to the pole A I The arrangement shown inFigure 5 is similar to that described with reference to Figure 4 exceptthat the laminations or strips which are of greater depth than the restare grouped together as at B to form a central ridge.

In the armature of which a portion is shown in Figure 6 the strips orlaminations are formed with serrations or teeth B and as shown thesepoints are staggered in adjacent strips so that the operating surface ofthe armature has a large number of tooth-like points projecting from it.

It will be understood that as the invention is intended for applicationto alternating current electromagnets the cores and armatures arepreferably always laminated although the laminations are only shown inFigures 2, 4t and 5 of the drawings.

It will be appreciated that in all the constructions thereare what maybe regarded as two or more'magnetic'circuits, one or more being ironcircuits, i. e. circuits with no air gap but with limited contact areaswhen the armature is against the p'ole and one or more other circuitshaving air gaps. This arrangement gives excellent results in practice inreducing chattering and vibration; i

What I claim as my invention and desire to secure by Letters Patentis 1. Annlternating current electromagnet in which-magnetic contactbetween the main surface of the pole and that of the armature isprevented by forming one of such surfaces with a lamination of magneticmaterial which projects beyond such main: surface.

2. An alternating current elcctromagnet in which magnetic contactbetween the main surface of the poleand that of the armature isprevented by forming one. of such surfaces with a plurality oflaminations of magnetic material which project beyond such main surface;

3. An alternating current electromagnet in which magnetlc contactbetween the main surface or the pole and that of the armature isprevented by forming one of such'surfaces with a plurality of toothed orserrated lamin-ati'ons of magnetic material which-project beyond suchmainsurface.

In testimony whereof I have signed my name to this specification;

PERCIVAL. FRANK HARRIS.

